Steam News has the announcement for Portal 2, the sequel to their highly regarded first-person puzzle platformer, saying it is due this holiday season. This follows on someviralhints that a Portal-related announcement was in the works, and the announcement has several characters underlined, seeming a further part of the alternate reality game surrounding the news. The highlighted characters are: "drattmannh0nee" if you want to puzzle through that one. Here's the announcement:

Valve, creators of best-selling game franchises (such as Left 4 Dead, Counter-Strike and Half-Life) and leading technologies (such as Steam and Source), today announced Portal 2 for shipment this coming holiday season.

Portal 2 is the sequel to 2007's Portal, which won 70 industry achievement awards.

Also, the April Cover Revealed on GameInformer.com has a Portal 2 image, saying: "Our 12-page cover story gives you the first details on Portal 2's new gameplay mechanics, storyline, and some surprising new twists." Update: A post on Kotaku has solved the latest clue in the ARG if you're ready to give up.